the violent earth. the san andreas fault the san andreas fault 1989 loma prieta quake 1989 loma...
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The Violent Earth
• The San Andreas faultThe San Andreas fault• 1989 Loma Prieta quake1989 Loma Prieta quake• 1906 San Francisco quake1906 San Francisco quake• 1964 Alaska earthquake1964 Alaska earthquake• 1811-1812 New Madrid quakes1811-1812 New Madrid quakes• 1995 Kobe, Japan, quake1995 Kobe, Japan, quake
Locked and creeping fault
segments
Creeping segmentCreeping segment
Seismicity along the San AndreasSeismicity along the San Andreas
Locked segmentLocked segment
Seismicity from the Seismicity from the 1989 Loma Prieta earthquake1989 Loma Prieta earthquake
Large gap in 20th century
Earthquake probability
TheSan Andreas
Fault
The San Andreas fault near Page Mill Road in Palo Alto
The San Andreas fault up close - not so impressive is it?
Offset streamsRight-lateral sense of motion
Off-set streams near Watsonville
The Carrizo Plain
Linear scars in the Carrizo Plain
Surface rupture in southern California
Bends in faults
Left bendLeft bend in a right- in a right-lateral fault yields a lateral fault yields a ridge ridge (compression)(compression)
Right bendRight bend in a right- in a right-lateral fault yields a lateral fault yields a basinbasin (extension) (extension)
The Dragon’s Back in the Carrizo Plain
Compressional ridgeCompressional ridge
Sag ponds
North American PlatePacific Plate
2 inches/year x 100 years= 200 inches
= 17 feet!
Multiple fault strands
The 1989 Loma Prieta earthquake
Loma Prieta Mercalli intensity
Three factors primarily determine what you feel in an earthquake:
1. Magnitude1. Magnitude You feel more intense shaking from a big earthquake than from a small one; big earthquakes also release You feel more intense shaking from a big earthquake than from a small one; big earthquakes also release
their energy over a larger area and for a longer period of time. their energy over a larger area and for a longer period of time.
2. Distance from the epicenter2. Distance from the epicenter Earthquake waves die off as they travel through the earth so the shaking becomes less intense farther Earthquake waves die off as they travel through the earth so the shaking becomes less intense farther
from the faultfrom the fault
3. Local soil conditions3. Local soil conditions Certain soils greatly amplify the shaking in an earthquake. Seismic waves travel at different speeds in Certain soils greatly amplify the shaking in an earthquake. Seismic waves travel at different speeds in
different types of rocks. Passing from rock to soil, the waves slow down but get bigger. A soft, loose soil different types of rocks. Passing from rock to soil, the waves slow down but get bigger. A soft, loose soil will shake more intensely than hard rock at the same distance from the same earthquake. The looser and will shake more intensely than hard rock at the same distance from the same earthquake. The looser and thicker the soil is, the greater the amplification will be, (e.g, Loma Prieta earthquake damage area of thicker the soil is, the greater the amplification will be, (e.g, Loma Prieta earthquake damage area of Oakland and Marina (SF) were 100 km (60 mi) and most of the Bay Area escaped serious damage). Oakland and Marina (SF) were 100 km (60 mi) and most of the Bay Area escaped serious damage).
(4. Building type) (4. Building type) The tops of high-rise buildings “feel” smaller earthquakes moreThe tops of high-rise buildings “feel” smaller earthquakes more
Soil type vs.
shaking intensity
Bay mud, etc.
Mud, silt, clay soils
Unconsolidated sediment
Weathered hard rock
Weathered sandstone
Shaking intensity for the 1906 earthquake
San Andreas M7.2 — San Francisco
Oakland’s Cypress structure (part of 880)
The 1906 rupture vs. the 1989 Loma Prieta
rupture
The 1906 quake wasmagnitude 7.7-7.9 on theRichter scale
The Loma Prieta quake was a 7.1 Richter magnitude
The 1906 San Francisco Earthquake
Actual slippage during the 1906 earthquake
Market Street
Looking west from Telegraph Hill
1906 quake damage
Santa Rosa city hall
Tomales Bay
Surface rupture during 1989 Loma Prieta quake
Building types vs. earthquake intensity
Masonry Multi-story
Wood-frame
Kobe, Japan — 1995
Seismicity in Japan vs. California
Kobe, Japan — 1995
Short, sharp pulselasting <15s recordedat seismic stations inrelatively solid rock
Strong, extended shakinglasting 2-3 minutes — nearthe coast on soft, thick, water-saturated soils
How shaking effects high-rise buildings
Mexico City
Cal State Northridge
Vertical & Horizontal Bracing
San Diego County
Oakland’s Cypress structure (part of 880)
Effect of Liquefaction
QuickTime™ and aYUV420 codec decompressorare needed to see this picture.
Marina District, San Francisco
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Liquefaction risk in the Bay Area
The Good Friday EarthquakeAlaska, 1964
Seismograph from the Good Friday earthquake
9.2 magnitude earthquake lasted 3-4 minutes(Loma Prieta lasted 17 seconds)
The tsunami moved things up to a mile inland
Control Tower, Anchorage Airport
The Basin and Range Province
New Madrid Earthquake1811-1812
Charleston — 1886
1886 earthquake near Charleston, South Carolina
Costs of various natural hazardsCompare hurricanes to earthquakes…